The present invention relates to an actuating device for a decompression valve of an internal combustion engine with cable starter, especially of an internal combustion engine of a hand-held working tool such as a motor chain saw, a cutter etc., wherein within the cylinder of the combustion engine a decompression valve is arranged the valve member of which is biased into its closed position. A transmission lever that is rotatable about its longitudinal axis is positioned with its longitudinal axis at a distance to the rotational plane of the cable drum of the starter cable and is positioned perpendicular to the rotational axis of the cable drum. A movement resulting from the rotation of the cable drum results in a first end of the transmission lever being rotated about its longitudinal axis so that a second end of the transmission lever performs an adjusting movement in the opening direction of the valve member.
From U.S. Pat. No. 3,687,124, an actuating device of the aforementioned kind is known with which the starting operation of an internal combustion engine to be started manually is to be facilitated by pressure release of the combustion chamber during the compression stroke. In the upper area of the combustion chamber a decompression valve is arranged that is comprised substantially of an axially movable valve member which closes an outlet channel. The valve member is forced into the closed position by a spring. For pressure release the valve member must be opened against the force of the spring. For this purpose, a transmission lever engages the valve member which transmits an axial coupling movement generated upon actuation of the cable starter of a coupling member onto the valve member and thus transfers the valve member into the open position. When the internal combustion engine is started, the coupling member, which is part of an overriding clutch, is axially returned so that the transmission lever is also returned and the valve member of the decompression valve closes. The combustion chamber of the cylinder is thus again tightly closed.
The control (adjusting) movement for opening and closing the decompression valve is derived from an axial movement of the coupling member. In a cable starter of a smaller constructive size, as used for hand-held working tools, an axially movable coupling part is not present so that the decompression valve cannot be actuated with the known device.
It is therefore an object of the present invention to provide an actuating device of the aforementioned kind for a decompression valve of a combustion engine with a cable starter such that even with a constructively small cable starter without axially displaceable component a simple and reliable automatic actuation of the decompression valve is possible.